discontinued - Micro

Micro-Metrics Company
OG232 Tooke Paint Inspection Gauge III
(discontinued)
Technical Data Sheet
Description and uses
Since its introduction in 1963, the Tooke Paint Inspection Gage
has become an essential tool for coatings application quality control
in both field maintenance painting and product finishing, Because it
performs a direct measurement of total film thickness as well as
thickness of individual coats (of contrasting colors), the Paint
Inspection Gage often finds use as a “referee” instrument and a
calibration tool for other instruments. In addition to measurement of
film thickness, the Tooke Gage can be used to measure adhesion of
films, and to observe microscopic checking and cracking, tendency
for brittleness, blistering, cratering, and other microscopic film
symptoms.
The Model III instrument the result of years of manufacture and
use ro provide reliability, precision, ruggedness, comfort and
convenience for all users in the lab and in the field.
The Tooke Gage has been used to assess sandblast cleaning
work, to measure plating thickness on ceramics, metal, and plastics.
and to measure thickness of protective backing films on mirrors. It is
virtually the only tool for measuring paint on plastics. Surface
contamination and wettability can be effectively visualized with the
illuminated microscope.
Specifications
Material and size:
Power:
Lamps:
Cutting Tips:
Carrying Case:
Shipping Weight:
Machined aluminum cylinder 2.5" diameter x 4.5" length;
50X illuminated, reticle 0-100 mils, 1-mil div.
Four AA dry cell batteries
Three GE No. 222
Tungsten carbide 0.620 x 0.132 x 0.072 in.
Suede-finished polyurethane cushioning
2 lbs, 3 oz
Ordering information
The Tooke Paint Inspection Gage III, OG232, is no longer available. The OG232 originally came
complete with illuminated microscope, three mounted cutting tips, felt tip marker, Allen wrench, carrying
case and instructions.
Micro-Metrics Company
4450 Ansley Lane
CUMMING, GA 30040-5252
www.micro-metrics.com
(Revised: 2013)
Principle
A small V-groove precision cut through the paint film and into the substrate is observed vertically with
an illuminated microscope bearing a measuring reticle. A schematic view of a cut is shown in Figure 1, below,
and the appearance under the microscope is shown in Figure 2 (next page). For the 45-degree cut illustrated,
film thickness is equal to the horizontally measured length of the layer of film. For any angle of cut:
Tooke Gauge Geometry
As shown in Figure 1 the observed
horizontal projection of the film in the
groove wall is related to the film
thickness by the equation:
At a 45-degree groove angle:
(A – AN) Finish coat thickness
(B – BN) Primer coat thickness
Figure 1 Geometry of Thickness Measurement
And:
Similarly, other groove angles may be cut for convenience and precision-of-measurement of coating films
over a wide range of thicknesses.
(A more-detailed explanation of Tooke Gauge geometry is available here: ww.micro-metrics.com/TDS-index.htm)
Cutting tip determination
Determine the cutting tip to be used in accordance with the following table:
Cutting tip designations and appropriate film thickness ranges
Cutting tip
Designation
Maximum coating
thickness in mils
Precision of thickness
determinations in mils
1 division on reticle
represents in mils
1×
100
± 0.25
1.0
2×
20
± 0.13
0.5
10×
3
± 0.025
0.1
If undecided use the 2× cutting tip.
Measurement procedure
Figure 2
Make a small mark with a marker (supplied with gage) at the
measurement location. Grasp the Paint Inspection Gage as shown
in Figure 3 with the selected cutting tip down on the painted
surface to form a “tripod” with its pair of guide studs.
Maintain moderate but continuous 3-point contact. and
draw the gage toward the body at a comfortable speed
directly across the marker “benchmark.”
Turn the microscope and view the inter-section of
the scribe and “benchmark. “ A momentary contact
(normally off) lamp switch prevents excessive battery
drain, but provides continuous illumination while the
gage is held for viewing. Line up a convenient long line
on the reticle directly over the left edge of the groove and
count small scale divisions (1 mil) inward toward the
central groove in the substrate. This count divided by the
tip designation (1×, 2×, or 10×) is the film thickness.
If the result should be less than 2 mils or more than 10 mils,
you may wish to use the 10× or 1× tips respectively.
Calibration
Original factory calibration is accomplished by setting
the guide studs in precise alignment with the cutting tips.
Checks are also made with precision applied film standards.
For highest precision work, the user is advised to maintain
painted panels of known thickness. and to check and
calibrate the instrument measurements periodically. After an
extended service period, if replacement of old tips fails to
restore a “zero” calibration, the instrument should be
realigned.
Suggestions to users:
1.
2.
3.
4.
5.
6.
On wood or other directional material make incisions in
the grain or “machine” direction to avoid ragged cuts.
Figure 3
Soft or elastic materials can sometimes be cooled or
frozen with ice or dry ice to obtain good cutting
characteristics.
Dyes or indicator solutions such as phenolphthalein are sometimes helpful to develop appearance
contrast between metals (iron-galvanizing) or paint coats.
“Wite-out®”-type fluid may be useful as a benchmarker on dark surfaces.
With some coatings, improved cuts can be achieved by wetting the surface, or by speeding or slowing the
cutting rate.
Coatings with poor adhesion will exhibit a ragged line at the substrate interface. Read thickness from the
left incision edge in the substrate in these cases. (Note reference 2 below.)
References
1.
2.
“A Paint Inspection Gage” by Raymond Tooke, Jr. Official Digest, July 1963, 691–698.
“Coatings Adherence Measurement By An Angular Scribe-Stripping Technique” by W. R Tooke, Jr. and J.
Montalvo, Journal of Paint Technology, January 1966, 38, pp. 18–28.
Gage Construction
The gage body, cap, and focusing ring are manufactured of machined aluminum. The lamp base is epoxy
plastic. The cylindrical body houses four AA bulbs in the annular space between the central (axial) microscope barrel and the cylinder wall. Three cutting tips are mounted radially in slots in the cylinder near the
upper (eyepiece) end. These are tightened by set screws tapped vertically into the cylinder and accessible
through holes in the cap. The slots positioned at 11, 12, and 1 o’clock positions, when viewed from above,
contain the 1×, 2×, and 10× cutting tips respectively. Each tip cooperates with one pair of four guide studs
mounted radially in the cylinder wall about 2 inches below the tips. The guide studs are tapped into the
cylinder wall and locked with hex nuts.
The three bulbs are arrayed on the lamp base to point inward from positions 120 degrees apart and
downward at approximate 45-degree angles to commonly illuminate on all sides a small area directly beneath
the microscope objective. The resultant intense illumination is adequate and comfortable even under most
adverse viewing conditions indoors or out.
Optional accessories
Replacement tungsten-carbide cutting tips:
Available in 1× (45E, OG200-1X), 2× (26.6E, OG200-2X),
5× (10.2E, OG200-5X), and 10× (5.7E, OG200-10X) configurations.
(5× cutting tip not shown.)
OG200-LED LED replacement bulb
The manufacturer says they should have a
“Long life, 50,000 hours.”
CTH01 (single) Cutting Tip Holder
The CTH01 Cutting Tip Holder, at a little under two inches (4.1cm) long, allows easy
use of a carbide cutting tip without having to manipulate the Tooke Gauge to make the
incision and then manipulate the gauge again to view the incision through the
microscope. Make multiple incisions with your most-used tip without
having to return the gauge to viewing position multiple times.
CTH02 (double) Cutting Tip Holder
This Cutting Tip Holder allows easy use of two cutting tip(s). Both cutting
tip holders include a carrying compartment that carries two extra tips (tips
not included).
MG402 Microgroover:
The Microgroover is a major accessory tool for creating coating incisions for
film thickness measurements with the Tooke Paint Inspection Gauge. This tool greatly extends the range of
the measuring technique to include almost any coating on any substrate. The Microgroover is especially
effective on hard and brittle (concrete) materials, as well as soft or elastomeric (rubber) substances. In
addition, fibrous composites are incised easily
and cleanly. This device eliminates
the deformations of coating and substrate that may occur when conventional gage
cutting tips are used.